Method of making hollow set-screws.



E N GARRISON METHOD OF MAKING HOLLOW SET scmzws.

APPLICATION FILED FEB. 6, 1914.

Patented June 2, 1914,

WI. 1 #yM UNITED STATES PATENT OFFICE.

EDWARD N. GARRISOIN, 0F BRIDGEPORT, CONNECTICUT, ASSIGNOR TO THE BURNS &

BASSICK COMPANY, OF BRIDGEPORT, CONNECTICUT, A CORPORATION OF CON-NECTICUT.

METHOD OF MAKING HOLLOW SET-SCREWS.

Specification of Letters Patent.

Patented June 2, 1914.

To all whom. it may concern Be it known that I, EDVARD N. Gxnniso s, acitizen of the United States, resid ng in the city of Bridgeport, countyof Fairfield, and State of Connecticut, have invented certain new anduseful Improvements in Methods of Making Hollow Set-Screws; and I dodeclare the following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art' to which itappertains to make and use the same.

My invention has reference to the method of making hollow screws, butmore particularly refers to a new method of making hollow set screwswhereby the completed article is rendered exceedingly strong and durableand is adapted to be operated by a suitable key or mandrel insertedtherein.

In the drawings Figures 1, 2, and 3, represent successive stages in thedrawing operations which are practised in carrying out my improvedmethod-Fig. 4 is a sectional elevation showing the position of partsimmediately prior to the swaging operat1on- Fig. 5 a view similar toFig. 4 butshowmg the position of parts after the swag1ng oper ation hasbeen effected-Fig. 6 a section at the line w, m, of Fig. 4-Fig. 7 a planview of the completed hollow screw, and Fig. 8 a sectional elevation ofthe completed screw.

Similar numerals of reference denote like parts in the several figuresof the drawing.

Heretofore hollow set screws have been made by forming the article bysuccessive drawing operations, the final drawing operation not onlyreducing the outside diameter but also giving the interior a polygonalform in cross section, but this method of making set screws renders themetal the least dense in the completed article, and therefore a threadcut on the exterior of such article is necessarily not as smooth as itwould be when the metal is dense and homogeneous.

My invention aims to make the set screw the strongest in its completedform, and the external diameter of the cup shaped blank remainsunchanged by the final or swaging operation. all of which will bereadily understood by the following description In carrying out myimproved method I draw a series of cup shaped blanks from flat sheetmetal, these blanks in their various stages being shown at Figs. 1, 2,and 3, respectively, the cup shaped blank shown at Fig. 3 illustratingthe final drawing operation, and these-blanks shown at 1, 2, and 3, arerespectively designated by the numerals ,1, 2, and 3. After the finaldrawing operation. the cup shaped blank 3 is placed within a die 4 and aswaging tool 5, whose lower portion is preferably hexagonal in crosssection as shown at'6, is inserted within this blank 3, and the size ofthe hexagonal portion 6 is such that the angular parts thereof fitsnugly against the inner wall of this blank 3.

That portion of the swaging tool which is formed into the hexagonalmember 6 is slightly reduced in diameter, so that a shoulder 7 is formedon the tool immediately above the hexagonal portion, and when the latteris contained within the blank 3, this shouldered portion will be abuttedagainst the upper edge of said blank, the diameter of the swaging toolbeing such that when said tool is forced downwardly it will readilyenter the die 4.

As the swaging tool is forced downwardly it will force the blank againsta convex knock-out plug 8 which extends upwardly through the bottom ofthe die so as to form a portion of the floor of the latter, thisknock-out plug being held in any suitable and ordinary manner. As theswaging tool is forced downwardly the bottom of the blank will be cuppedinwardly owing to its contact against the plug 8, and the continuedmovement of the swaging tool will cause the metal of the blank 3 to beswaged so as to completely fill the spaces between the inner wall of theblank 3 and the flat surfaces of the hexagonal member, and at the sametime the length of the blank 3 will of course be reduced and the bottomof the hexagonal form 6 will seat firmly against the bottom of the blankand will cause a thickening or swagin'g of the completed article. Itwill thus be observed that the outside diameter of the blank 3 has notbeen disturbed, while the swaging operation has caused the metal to flowfreely around the hexagonal member and to thereby impart a hexagonalshape to the inner wall of the screw blank thus formed, as shown at 12.

When the swaging tool has been withdrawn, the knockout plug 8 is thrustupwardly in any ordinary manner so as to discharge the completely formedscrew blank from the die, and in the completed article the bottomportion will have a concavity 13 whose walls meet the external walls ofsuch article so as to form asharp edge, this edge being Very desirablein order to afford a proper bite of the set screw when the latter isdriven home to perform its function.

The little spaces referred to between the inner Wall of the blank 3 andthe flat surfaces of the hexagonal member 6, which are filled in by theswaging operation above described are clearly shown at Fig. 6 and aredesignated by the numeral 9. At Fig. 7 the completed article isdesignated by the numeral 10, and the-thickened portions of the screwwill readily be perceived.

After the formation of the screw blank by the swaging operation abovedescribed, such screw blank is externally threaded as shown at Fig. 8,the threaded portion being designated by the numeral 11.

The article heretofore made, in its final form, is the same inallrespects as the completed article formed by my method, but heretofore ithas been necessary to employ much thicker metal in the drawing operationin order to produce the completed article by a final drawing and yet topreserve the proper thickness of such article. But in my improvement thedrawing operation is greatly simplified, and less power is consumedbecause I am enabled to use a far thinner metal, since the properthickness of the completed article is produced by a swaging operationwhich latter also makes the screw blank the densest and therefore thestrongest in its completed form.

Having thus described my invention what I claim as nev and desire tosecure by Letters Patent is 1. The method of making hollow screws, whichconsist-s of forming a cylindrical shell closed atthe bottom and withthe outside diameter equal to that of the completed article, reducingthe length of said shell by a swaging operation performed around apolygonal shaped member Whose angular portions snugly fit within saidshell, and

' finally externally threading said shell.

2. The method of making hollow screws, which consists in forming acylindrical shell closed at the bottom and with an outside diameterequal to that of the completed article, reducing the'length of saidshell by. a swaging operation performed around a polygonal shaped memberwhose angular portions snugly fit within said shell and simultaneouslythickening the bottom of said shell and forming in the external surfacethereof a concavity, and finally externally threading said shell.

In testimony whereof I afiix my signature in presence of two witnesses.

EDWARD N. GARRISON. Witnesses:

CHARLES E. WARD, A. E. BELISLE.

